Effect of photoperiod on steroid metabolism in the sea star Asterias Rubens L

Abstract

1. 1. The effect of photoperiod on steroid metabolism in Asterias rubens was studied. 2. 2. Daylength was artificially shortened in 3 weeks from long-day (LD 18/6) to short-day (LD 6/18) conditions and its effect on the metabolism of pregnenolone and dehydroepiandrosterone was studied in homogenates of gonad and pyloric caeca tissue from male and female seastar. 3. 3. Pregnenolone metabolism did not change during the experiment when the animals were kept continuously under the same (long-day) conditions. Pregnenolone metabolism was intensified by decreasing daylength. The production of progesterone reached its maximum at a daylength comparable to that in autumn (LD 12/12), and that of an unidentified steroid at an even shorter daylength. 4. 4. Metabolism of dehydroepiandrosterone was influenced by photoperiod. There were indications that androstenedione production is maximal at fall conditions. This was evident for an as yet unidentified steroid. 5. 5. Metabolism of DHEA strongly increased during the experiment in animals which were kept continuously under long-day conditions. It is discussed that this may be a reaction to crowding. © 1991.